The invention relates generally to hammer mills, and more particularly to a process for refurbishing the discs of a hammer mill after substantial wear necessitates removing the discs from service.
Hammer mills, which are also known as “hammer breakers”, are machines used for crushing or shredding items, such as automobiles, scrap metal and paving materials, into smaller pieces, a process referred to as comminution. A typical hammer mill is shown in U.S. Pat. No. 4,056,232 to Linnerz et al., which is herein incorporated by reference. Hammer mills have a stationary housing in which a rotor body is rotatably mounted. The rotor body consists of a plurality of discs rigidly connected to a rotor shaft. Each of the discs of some hammer mills weighs about 9000 lbs. Rods extend through the discs and are spaced radially from, and extend parallel to, the rotor shaft. Massive hammers are pivotably mounted between the discs on the rods. The hammers are thus pivotably mounted axially of the rotor shaft on the rods in a circumferentially spaced relationship around the periphery of the discs. Comminution occurs when the hammers impact the object that is fed into their path. As the material breaks up, it passes out of the hammer mill. Because the rotor shaft rotates at about 600 revolutions per minute (rpm), each hammer swings at about 200 miles per hour against the object in its path.
If the material to be comminuted is abrasive, the outer surfaces of the discs will be subjected to considerable wear and will become worn by the impinging material. During their lifetimes, discs lose significant amounts of metal from their peripheral edges. Because of this, the discs become no longer usable and must be replaced. Conventional replacement involves removing a worn disc and replacing it with a new disc. Because this is a very expensive replacement, the need arises for another way of replacing worn discs without the waste involved in discarding or merely recycling the worn disc.